What Was This Mystery Pyramid?

This bizarre pyramid in North Dakota, circa 1975, may look like something out of a lost Stanley Kubrick film, but it's actually the facility that warmed up the Cold War. Well, for a little while, anyway. These incredible images from the Library of Congress show the Stanley R. Mickelsen Safeguard Complex near the town of Grand Forks -- America's first operational ABM (anti-ballistic missile) defense system. The pyramid is actually the facility's missile site control building.

Library of Congress

Part of the U.S. Army's Safeguard anti-ballistic missile program, the facility employed a phased array radar -- rather than a large dish, the central structure had thousands of small antenna built into each face. The columns in the foreground are exhaust ports for the underground missile silos.

Library of Congress

A view of the of missile site control building turret wall during early construction, illustrating the massive amount of rebar utilized in the project. The facility would later provide launch and control for 30 long-range and 70 short-range anti-ballistic missiles, designed to shoot down incoming ICBMs.

Library of Congress

A view of missile site control building interior, with workmen installing an inspection fixture on the antenna array support ring.

Library of Congress

A later view of missile site control building. That rounded cylinder on the right was actually an escape tunnel, eventually buried underground.

Library of Congress

A photographic copy of original U.S. Army Corps of Engineers design drawing, dated January 1970, and revised in January 1974. All facilities were nuclear hardened -- designed to withstand a nearby nuclear blast, but not a direct hit.

Library of Congress

The view from south to north, with diesel generators and exhaust and intake towers. The Mickelsen Safeguard Complex was only in operation for less than a year -- April 1975 to February 1976 -- before it was deactivated. It was abandoned for decades and left to the elements. In 1991, several buildings on the site were dismantled or destroyed, but in its brief hey-day, its very construction was considered key to getting Soviet cooperation with the 1972 Anti-Ballistic Missile Treaty.